Sound communication system

ABSTRACT

A multipurpose sound communication system for use anywhere. This system may thus be used in a number of ways not described in the specification, but will be found useful in many, if not all, emergency vehicles including, but not limited to, ambulances and police patrol cars. The system employs one voltage controlled oscillator (VCO) with six selectively adjustable inputs. One of the inputs if OFF. Three inputs provide different corresponding siren sounds. One input places the radio on the speaker. Another input provides for public address and manual control of the siren. Speaker assembly negative feedbacks are provided for signal balance. Two negative feedbacks are selectively provided. A manual control circuit provides ramp voltages for siren control through the VCO. A transistor switch is driven to cut-off to prevent VCO operation when the siren frequency falls below a predetermined frequency.

United States Patent [19] Carroll [451 May 6,1975

[ SOUND COMMUNICATION SYSTEM [75] Inventor: Gordon S. Carroll, Costa Mesa,

Calif.

[73] Assignee: International Telephone &

Telegraph Corporation [22] Filed: Aug. 2, I973 {21] Appl. No; 384,889

[52] US. Cl. 179/1 R; 340/384 E [51] Int. Cl. G081) 3/10 [58] Field of Search 179/1 B, 1 R, 1 SW, 1 AA, 179/1 F, 1 VL, l A, 340/384 R, 405, 389 E;

[56] References Cited UNITED STATES PATENTS 2,358,630 9/1944 Fay 179/1 F 2,396,422 3/1946 Hines 340/405 3,014,199 12/1961 Dill et a1. 340/384 E 3,051,944 8/1962 Smith 340/384 E 3,130,396 4/1964 Hughes et a1. 340/384 E Primary Examiner-Kathleen H. Claffy Assistant ExaminerTommy P. Chin Attorney, Agent, or Firm- A. Donald Stolzy CONT/202.

RAD/O [57] ABSTRACT A multipurpose sound communication system for use anywhere. This system may thus be used in a number of ways not described in the specification, but will be found useful in many, if not all, emergency vehicles including, but not limited to, ambulances and police patrol cars. The system employs one voltage controlled oscillator (VCO) with six selectively adjustable inputs. One of the inputs if OFF. Three inputs provide different corresponding siren sounds. One input places the radio on the speaker. Another input provides for public address and manual control of the siren. Speaker assembly negative feedbacks are provided for signal balance. Two negative feedbacks are selectively provided. A manual control circuit provides ramp voltages for siren control through the VCO. A transistor switch is driven to cut-off to prevent VCO operation when the siren frequency falls below a predetermined frequency.

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I vml SOUND COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION This invention relates to electronic gear for use with loudspeakers, and more particularly, to a multipurpose apparatus for use on emergency vehicles or elsewhere.

In the past, loudspeaker gear for police patrol cars, for example, have been complicated and expensive. The number of possible functions thereof have also been limited.

SUMMARY OF THE INVENTION In accordance with the system of the present invention, the above-described and other disadvantages of the prior art have been overcome by providing a communications system in which a voltage controlled oscillator (VCO) serves a plurality of functions.

The above-described and other advantages of the present invention will be better understood from the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which are to be regarded as merely illustrative:

FIG. 1 is a block diagram of a sound communication system constructed in accordance with the present invention;

FIG. 2 is a schematic diagram of a power supply assembly constructed in accordance with the present invention;

FIG. 3 is a schematic diagram ofa multivibrator hereinafter called an AUTO MV;

FIG. 4 is a schematic diagram of a multivibrator hereinafter called a Hl-LO MV;

FIG. 5 is a schematic diagram of a manual control circuit constructed in accordance with the present invention;

FIG. 6 is a schematic diagram of a voltage controlled oscillator hereinafter referred to as a VCO:

FIG. 7 is a schematic diagram of first and second amplifier stages;

FIG. 8 is a schematic diagram of a driver;

FIG. 9 is a schematic diagram ofa speaker assembly;

FIG. 10 is a schematic diagram of a microphone assembly;

FIG. 11 is a schematic diagram ofa control assembly; and

FIGS. 12,13,14,15, l6 and 17 are graphs ofa group of waveforms characteristic of the operation of the sound communication system of the present invention illustrated in FIGS. l-I l, inclusive.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, in FIG. 1, a sound communication system 20 is shown including a power supply assembly 21, an mean MV 22, a HI-LO MV 23, a YELP MV 24, a manual control circuit 25, a VCO 26, a first amplifier stage 27, a second amplifier stage 28, a driver 29, a speaker assembly 30, a control assembly 31, a radio 32 and a microphone assembly 33.

Power supply assembly 21 has output leads 35, 36 and 37 which are maintained at potentials V1, V2 and V3, respectively. The lead 35 of potential V1 is connected to AUTO MV 22, l-ll-LO MV 23, YELP MV 24, manual control circuit 25, VCO 26, first amplifier stage 27 and second amplifier stage 28. The lead 36 of potential V2 is connected to AUTO MV 22, Hl-LO MV 23, YELP MV 24, VCO 26, first amplifier stage 27, second amplifier stage 28 and driver 29. The lead 37 of potential V3 is connected to AUTO MV 22, YELP MV 24, manual control circuit 25, first amplifier stage 27 and to control assembly 31.

Power supply assembly 21 has a lead TB1-2 connected to speaker assembly 30, leads C and 14-1 connected to control assembly 31, and leads 12-3 and 12-4 connected to microphone assembly 33.

The VCO 26 has output leads 13-20A and 13-20B connected to power supply assembly 21 and to control assembly 31, respectively. The VCO 26 has an input lead 13-21 connected from control assembly 31.

The AUTO MV 22 has an output lead 13-23 connected to control assembly 31.

The HI-LO MV 23 has an output lead 13-22 connected to control assembly 31.

The YELP MV 24 has an output lead 13-19 connected to control assembly 31.

The manual control circuit 25 has an input lead 13-14 and two output leads 13-16 and 13-18 connected to control assembly 31.

First amplifier stage 27 has input leads 13-2 and 13-3 connected from control assembly 31, and an output lead 51.

A lead 12-1 is connected from microphone assembly 33 to first amplifier stage 27.

The output lead 51' of first amplifier stage 27 serves as an input lead of second amplifier stage 28. A lead D connects the output of second amplifier stage 28 to the input of driver 29.

Leads TB2-9, TB2-l0 and 14-2 connect the outputs of driver 29 to speaker assembly 30.

Speaker assembly 30 has output leads P1-13A and p1-I3b connected to microphone and control asssemblies 33 and 31, respectively.

Radio 32 has one side grounded at 40 and has an output lead 41 which is connected to control aassembly 31.

Power supply assembly 21 is illustrated in FIG. 2 including a relay 51 including a winding 52, a pole 53 and a contact 54.

Junctions are provided at 55, 56, 57, 58, 59 and 60. A DC. source of potential is provided at 61 having a positive terminal 62 and a negative terminal 63. The negative terminal 63 is grounded at 64. Junctions 59 and 60 are connected from terminal 63.

A diode 65 is connected from a junction 66 to junction 55, and is poled to be conductive in a direction toward junction 55. Junctions 55 and 56 are connected together. Similarly, junctions 57 and 58 are connected together.

A resistor 67 is connected between junctions 55 and 57. A resistor 68 is connected between junctions S7 and 59. A capacitor 69 is connected between junctions 56 and 58. A capacitor 70 is connected between junctions 58 and 60.

Junctions are also provided at 71 and 72. Pole 53 is connected from junction 71. Contact 54 is connected to a junction 73. Lead C is connected from junction 73 to lead C of control assembly 31 shown in FIG. 11.

Lead TB1-2 is connected from junction 73 to lead TB1-2 of speaker assembly 30 shown in FIG. 9.

A lead 12-3 is connected from junctions 66 and 72 to lead 12-3 of microphone assembly 33 shown in FIG. 10.

A lead 14-1 is connected from junction 72 to lead 14 of control assembly 31 shown in FIG. 11. A dotted box 74 includes a potentiometer 75 and a main power switch 76. The main power is turned off by opening switch 76. Switch 76 has a pole 77 which is connected from junction 72, and a contact 78 connected from junction 71. Potentiometer 75 has a winding 79 and a wiper 80. Movement of potentiometer wiper 80 on winding 79 adjusts the volume which is produced when the microphone assembly 33 is employed as a combina tion public address system.

Potentiometer wiper 80 is ganged with pole 77 of switch 76. A resistor 81 is connected from a lead 13- 20A to potentiometer wiper 80. Lead J3-20A, in FIG. 2, is connected from lead J3-20A of VCO 26 shown in FIG. 6.

The AUTO MV 22 is illustrated in FIG. 3. The AUTO MV has various junctions 82, 83, 84, 85, 86, 87, 88 and 89.

Junctions 82 and 83 are maintained at potential V2. A capacitor is connected between junctions 82 and 84. A differential amplifier 91 is illustrated in FIG. 3 having inverting and non-inverting input leads 92 and 93, respectively.

Amplifier 91 also has positive and negative power input leads 94 and 95 connected to potentials V1 and V3, respectively.

Inverting input lead 92 is connected from junction 84. Non-inverting input lead 93 is connected from junction 85.

A resistor 96 is shown in FIG. 3 connected between junctions 84 and 86.

Amplifier 91 has an output lead 97 connected to junction 86. Junctions 86 and 87 are connected together. A resistor 98 is connected between junctions 85 and 87. A resistor 99 is connected between junctions 83 and 85. A resistor 100 is connected between junc' tions 87 and 88. A capacitor 101 is connected from junction 88 to junction 83. A resistor 102 is connected between junctions 88 and 89. A resistor 103 is con nected from junction 89 to potential V1. A lead 13-23 is connected from junction 89 to lead 13-23 of control assembly 31 shown in FIG. 11.

HI-LO MV 23 is shown in FIG. 4 having junctions 104, 105,106, 107,108, 109 and 110. Again, an amplifier 111 is provided with inverting and noninverting input leads 112 and 113, respectively. Amplifier 111 also has a positive power input lead 114 connected to potential V1, and an output lead 115 connected to junction 108. A capacitor 116 is connected between junctions I06 and 104. Junctions 104 and 105 are connected to potential V2. The amplifier inverting input lead 112 is connected from junction 106. The noninverting input lead 113 is connected from junction 107. A resistor 117 is connected between junctions 105 and 107. A resistor 118 is connected between junctions 107 and 109. A resistor 120 is connected between junction 106 and 108. A resistor 121 is connected between junctions I08 and 109. Junctions I09 and 110 are connected together. A resistor 122 is connected fromjunction 110 to potential V]. A lead J3-22 is connected from junction 110 to the same lead 13-22 of control assembly 31 shown in FIG. 11.

Manual control circuit 25 is shown in FIG. 5 includ ing junctions 123, 124, 125, 126, 127, 128 and 129.

A resistor is connected from junction 125 to potential V1. Junctions 123 and 124 are connected to potential V3.

As used herein, the phrase connected to potential" is hereby defined to mean connected to a member including, but not limited to, a conductive lead or a conductive junction which has a potential."

In FIG. 5, a resistor Ra is connected from junction 123 to junction 125. A PNP transistor 134 is provided in FIG. 5 having a collector 135, an emitter 136 and a base 137. A resistor 138 is connected from the base 137 of transistor 134 to junction 126, junctions 125 and 126 being connected together. A diode 138 is connected between junctions 126 and 127 and is poled to be conductive in a direction toward junction 127.

Junctions 127, 128 and 129 are connected together. Transistor emitter 136 is connected from junction 128. A capacitor C is connected from junction 127 to tran sistor base 137. A resistor 139 is connected between junction 124 and 129. A capacitor 140 is connected from junction 129 to potential V2.

A lead 13-14 is connected from junction 129 to the same lead 13-14 of control assembly 31 as shown in FIG. 11.

A resistor 14] is connected from junction 128 to lead 13-16. Lead J3-16 is connected to the same lead 13-16 of control assembly 31 shown in FIG. 11. A resistor 142 is connected from transistor collector 135 to a lead 13- IS. Lead 13-18 is connected to the same lead 13-18 of control assembly 31 shown in FIG. 11.

VCO 26 is illustrated in FIG. 6 having junctions 143, 144, I45, I46 and 147.

A lead 13-21 is connected from the same lead 13-21 of control assembly 31 shown in FIG. 11 to junction 143.

Again, a differential amplifier 148 is provided with an inverting input lead 149, a noninverting input lead 150, a positive power input lead 151 and an output lead 152. Inverting input lead 149 is connected from junction 143. Non-inverting input lead 150 is connected to potential V2. Positive power input lead 151 is connected to potential V1. junctions 143 and 144 are connected together. A capacitor 153 Junctions connected between junctions 144 and 145. A unijunction transistor 154 is provided having a first base 155, a second base 156 and an emitter 157. Transistor emitter 157 is connected from junction 144. First base is connected from junction 145. A resistor 158 is connected from second base 156 to potential V1.

Junctions 145 and 146 are connected together. A resistor 159 is connected in series with a capacitor 160 from junction 146 to junction 147. A lead 13-20B is connected from junction 147 to the same lead .l3-20B of control assembly 31, shown in FIG. 11.

A lead 13-20A is connected from junction 147 to the same lead 13-20A of power supply assembly 21 shown in FIG. 2.

The first and second amplifier stages 27 and 28, re spectively, are shown in FIG. 7.

The first amplifier stage 27 has an input lead 13-2 connected from the same lead 13-2 of control assembly 31 shown in FIG. 11.

First amplifier stage 27 has junctions 44, 161, 162, I63, 164 and 175. Lead 13-2 from control assembly 31 is connected to junction 161 via a capacitor Ca and junction 175.

First amplifier stage 27 also has the input lead J2-1 and an input lead 13-3 connected together at junction 44. A capacitor 186 and a resistor 185 are connected in series between junctions 44 and 175.

Again. first amplifier stage 27 includes an amplifier 165 with an inverting input lead 166, a non-inverting input lead 167, positive and negative power input leads 168 and 169 and an output lead 170.

lnverting input lead 166 is connected from junction 161. Non-inverting input lead 167 is connected to potential V2. Junctions 161 and 162 are connected together. A resistor 17] and a capacitor 172 are connected in parallel between junctions 162 and 163.

Positive and negative power input leads 168 and 169 are connected respectively to potentials V1 and V3. Amplifier output lead 170 is connected to junction 164. Junctions 163 and 164 are connected together.

As stated previously, the first and second amplifier stages 27 and 28, respectively, are connected over lead 51.

Second amplifier stage 28 has various junctions 173, I74, 176 and 177.

A capacitor 178 and a resistor 179 are connected in series from lead 51 to junction 173. Junctions 173 and 174 are connected together. An amplifier 180 is provided having an inverting input lead 181, a noninverting input lead 182, a positive power input lead 183 and an output lead 184. Non-inverting input lead 182 is connected to potential V2. Inverting input lead 181 is connected from junction 175. Positive power input lead 183 is connected to potential V1. Output lead 184 is connected to junction 177.

Lead J2-l of FIG. 7 is connected from the same lead 12-1 of microphone assembly 33, shown in FIG. 10. Lead 13-3 of FIG. 7 is connected from the same lead 13-3 of control assembly 31, shown in FIG. 11.

In FIG. 7, second amplifier stage 28 has a resistor 187 and a capacitor 188 connected in parallel between junctions 174 and 176. Junctions 176 and 177 are connected to a lead D which also connects with the same lead D of driver 29 shown in FIG. 8.

Driver 29 is shown in FIG. 8 including a transformer 189 having a primary winding 190 and a secondary winding 191. Winding 190 has leads 192 and 193. Winding 191 has leads 194 and 195.

Winding lead 192 is connected from lead D which, in turn, is connected from the same lead D of second amplifier stage 28 shown in FIG. 7.

Winding lead 193 is also connected to potential V2.

Other various junctions are shown throughout the circuit of FIG. 8 including junctions 198, 199, 200, 201, 202, 203 and 204. A resistor 205 is connected between junctions 198 and 199. Winding lead 194 is connected to junction 198. Winding lead 195 is connected to junction 200. A resistor 206 is connected between junctions 199 and 200. Junction 199 is connected to potential V3. Transistors 207, 208, 209, 210, 211 and 211' are shown in FIG. 8.

Transistor 207 has a collector 212 connected to junction 201, an emitter 213 and a base 214 connected from junction 198.

Transistor 208 has a collector 215 connected from junction 201, an emitter 216 and a base 217 connected from emitter 213. Junctions 201 and 202 are connected together. Similarly, junctions 203 and 204 are connected together.

Transistor 209 has a collector 218 connected to junction 202, an emitter 219 and a base 220 connected from emitter 216.

Transistor 210 has a collector 221 connected to junction 203, an emitter 222 and a base 223 connected from junction 200.

Transistor 211 has a collector 224 connected to junction 203, an emitter 225 and a base 226 connected from emitter 222.

Transistor 211 has a collector 227 connected to junction 204, an emitter 228 and a base 229 connected from emitter 225.

A lead TB2-10 is connected from emitter 228 to the same lead TB2-10 in speaker assembly 30 shown in FIG. 9.

A lead 14-2 is connected from junctions 202 and 204 to the same lead 14-2 of control assembly 31 shown in FIG. 11.

A lead TB2-9 connected from emitter 219 is connected to the same lead TB2-9 of speaker assembly 30 shown in FIG. 9.

Speaker assembly 30 is shown in FIG. 9 including junctions 230, 231, 232, 233 and 236.

A lead TB2-9 is connected from the same lead TB2-9 of driver 29, shown in FIG. 8, to junction 230.

A lead TB2-10 is connected from the same lead TB2- IQ of driver 29, shown in FIG. 8, to junction 233.

A resistor 237 is connected between junctions 230 and 231. A resistor 238 is connected between junctions 232 and 233.

Transistors 239 and 240 are also provided. Transistor 239 has a collector 242 connected to junction 231, an emitter 241 connected to one end 251 of a primary winding 249 of a transformer 247. Transistor 239 also has a base 243 connected from junction 230, junctions 231 and 232 being connected together. Junction 232 is connected to potential V3.

Transistor 240 includes a collector 245 connected to junction 232, an emitter 244 connected to the other end 252 of winding 249, and a base 246 connected to junction 233.

The transformer 247 has a secondary winding 250.

Transformer secondary winding 250 has a lead 253 connected to junction 47 via lead 46, a junction being provided at 254 which is connected from lead 253 and connected to one side ofa speaker 248 over a lead 255.

Secondary winding 250 has a lead 256 which is connected to junction 236. Junction 236 is connected to the other side of speaker 248 over a lead 257.

A capacitor Cb is connected from junction 236 to ground.

Microphone assembly 33 is shown in FIG. 10 including a double-pole, single-throw switch 258.

Switch 258 has poles 259 and 260 and respective contacts 261 and 262 therefor.

Pole 259 is connected from lead 12-1 that is connected to the same lead 12-1 of the second amplifier stage 28 shown in FIG. 7.

Pole 260 is connected from lead 12-3 which is, in turn, connected from the same lead 12-3 of power supply assembly 21 shown in FIG. 2.

Contact 261 is connected from lead Pl-13A which, in turn, is connected from the same lead Pl-13A of speaker assembly 30 whocn in FIG. 9.

A microphone 263 is connected from contact 262 to lead 12-4, which lead is, in turn, connected to the same lead 12-4 of power supply assembly 21 shown in FIG. 2.

Control assembly 31 is shown in FIG. 11 including leads 13-16, 14-1, 14-2, 13-18, 13-14, 13-23, 13-19, 13- 22, 13-21, 13-208, 13-2 and 13-3, all of which are connected to or from leads of the same reference characters respectively illustrated in FIGS. 5, 2, 8, 5, 5, 3, I, 4, 6, 6, 7 and 7.

A switch is provided at 264. Switch 264 is a conventional momentary contact switch which is spring biased open and is, therefore, normally open.

Switch 264 has contacts 265 and 266 connected respectively to leads 13-16 and a junction 267.

Other junctions are provided at 267, 268, 269 and 270. A lamp 271 is connected between junctions 267 and 268. Two lamps 272 and 273 are connected in parallel between junctions 269 and 270. Junctions 268 and 269 are connected together. Junction 268 is maintained at potential V3. Lead C is connected to junction 270 from the same lead C of power supply assembly 21 shown in FIG. 2.

Also shown in FIG. 11 are three switches 271, 272 and 273 which have respective poles 274, 275 and 276.

The switches 271, 272 and 273 are ganged. Each of the switches 271, 272 and 273 is a six-position switch.

Switch 271 has contacts 277, 278, 279, 280 and 281.

Switch 272 has contacts 282, 283, 284, 285, 286 and 287.

Switch 273 has a contact 288.

Pole 274 of switch 271 is connected to the lead 13- The pole 275 of switch 272 is connected to the lead 13-2.

The pole 276 of switch 273 is connected from the lead P1-13B connected from the same lead P1-13B of speaker assembly 30 shown in FIG. 9.

Other junctions 289, 290 and 291 are shown in FIG. 11, all three of these junctions being connected together. Lead 13-208 and contact 282 of switch 272 are connected from junction 289. Junctions 290 and 291 are connected respectively from contacts 285 and 286. Junction 291 is also connected to contact 287. A resistor 292 is connected from contact 283 to radio 32 shown in FIG. 1 over lead 41.

The voltage which appears at junction 89 in FIG. 3 is illustrated in FIG. 12. The fundamental of the waveform of FIG. 12 may have a period equal to T... In a typical example, T might be 8.0 seconds.

The voltage which appears on lead 13-22 shown in FIG. 4 is illustrated in FIG. 13. The period T,, of the waveform shown in FIG. 13 may typically be 2.0 seconds.

The YELP MV may be identical to the AUTO MV, if desired, with the exception that some circuit values may change. The voltage which appears on lead 13-19 shown in FIG. 1 at the output of the YELP MV 24 is illustrated in FIG. 14. In this illustration, the fundamental period T, may be, for example, 0.5 seconds.

Transistor 134, shown in FIG. 5, acts substantially as a switch and is maintained either at cut-off or at saturation. That is, the transition from cut-off to saturation and vice versa is made very rapidly.

When the button of switch 264 in FIG. 11 is depressed, contacts 265 and 266 are connected together. When the switches 271, 272 and 273 are in the proper (leftmost) position, the depression of the button of switch 264 will cause junction 128 to change in potential as illustrated in FIG. 15 from V, to V Since a voltage similar to that shown in FIG. 15 is applied to the input of the VCO 26, the frequency of the output signal of VCO 26 will change in accordance with the solid line waveform shown in FIG. 15.

In general, transistor 134 in FIG. 5 cannot turn on until the voltage of junction 128 has risen somewhat. For example, it may rise to a point 293 shown in FIG. 15.

In FIG. 15, dotted line 294 may be considered ground or V3, if desired.

When the button of switch 264 in FIG. 11 is no longer depressed, the potential of junction 128 in FIG. 5 may then fall as indicated by the solid lines in FIG. 16. Transistor 134 prevents the VCO 26 from producing an output signal of a frequency below a predetermined minimum. The falling potential at 128 in FIG. 5 thus no longer affects the operation of the VCO 26 to the right of point 295 in FIG. 16 because transistor 134 is driven to cut-off at point 295.

The output voltage of VCO 26 which can appear at junction 146 in FIG. 6 may have a wave shape as shown in FIG. 17.

In order to make the foregoing as clear as possible, it should be stated that all the functions illustrated in FIGS. 12-I7, inclusive, are potentials which are graphed as different functions of time.

In FIGS. 15 and 16, the following relations may or may not be used, as desired:

The term V may or may not be equal to 6 volts, as desired.

At V,,., V, and at V the frequency of the output signal of the VCO 26 may or may not be 500 hertz and 1,500 hertz, respectively, as desired.

The output signal of VCO 26 may be saw-tooth or any other periodic wave.

AUTO MV 22, I-II-LO MV 23 and YELP MV 24 all may be conventional MV's, or they may be as shown in FIGS. 3, 4 and 3, respectively, with the changes to be noted hereinafter.

When pole 274 of switch 271 in FIG. 11 is placed in engagement with contact 277, the output of manual control circuit 25 on lead 13-18, shown in FIG. 5, is connected to the input of VCO 26 over the lead 13-21 shown in FIG. 6.

In FIG. 2, diode 65 protects all portions of the circuits connected from junctions 56, 58 and 60 when battery 61 is connected between terminals 62 and 63 with the wrong polarity.

Capacitor 69 provides a small amount of voltage regulation.

As shown in FIGS. 3 and I1, AUTO MV 22 has an output on lead 13-23 which is connected to control assembly 31 in FIG. 11. YELP MV 24 may be identical to AUTO MV 22, shown in FIG. 3, except for the changes in circuit values, to be described.

In FIG. 4, the output of I-II-LO MV 23 is connected to control assembly 31 of FIG. 11 over lead 13-22.

In FIG. 5, when the potential of junction 129 rises above the potential of junction 126, transistor 134 is driven to saturation. In this state, transistor 134 is a closed switch.

When the potential of junction 129 falls below the potential of junction 126, transistor 134 is cut off and any output signal on lead 13-18 connected to the input of VCO 26 is prevented. In this case, transistor 134 is an open switch.

When switch 264 in FIG. 11 is closed, 6 volts, for example, are impressed upon lead 13-16 in FIG. connected to resistor 141. Capacitor 140 then charges, and the potential ofjunction 129 rises to a maximum of, for example, 6 volts above line 294 in FIG. 15, ie. to, for example, V

When switch 264 in FIG. 11 is opened, capacitor 140, in FIG. 5, partially discharges through resistor 139 (see FIG. 16). Thus, lead 13-14 in both FIGS. 5 and 11 is the same lead and connects junction 129 in FIG. 5 to contact 278 of switch 271 in FIG. 11.

In power supply assembly 21 of FIG. 2, lead 14-1 connected from positive terminal 62 of DC. source of potential 61 through switch 76, lead 14-1 thus supplying a positive potential to switch contact 266 of switch 264 in FIG. 11. The positive potential of contact 266 of switch 264 is then transferred to contact 265 of lead 13-16 when switch 264 is closed, lead 13-16 being the same lead in both FIGS. 5 and 11 and connecting resistor 141 in FIG. 5 to contact 265 of switch 264.

In FIG. 6, the input to VCO 26 is supplied over lead 13-21. The output of VCO 26 is supplied over leads 13- 20A and 13-20B.

First amplifier stage 27 receives negative feedback over lead 13-3. This is added to the input on lead 13-2 via the arrangement of amplifier 165 and resistors 159, 185 and 171 (analog adder). The output of first amplifler stage 27 is connected to the input of second amplifier stage 28 over a lead 51. First amplifier stage 27 has an input lead 13-2. Second amplifier stage 28 has an output lead D. See FIG. 7.

First amplifier stage 27 receives negative feedback of lead in two ways. This negative feedback is supplied over lead 12-1 and over lead 13-3. The feedback over lead 12-1 comes from lead P1-13A of speaker assembly 30 (FIG. 9) through switch 258 to lead 12-1, shown in FIG. 10.

Negative feedback is supplied over lead 13-3 from lead P1-13B of speaker assembly 30 (FIG. 9) to lead 13-3 in control assembly 31 of FIG. 11.

Leads TB2-l0, TB2-9 and 14-2 connect the outputs of driver 29 shown in FIG. 8 to speaker assembly 30 (FIG. 9).

Driver 29 of FIG. 8 receives an input signal over lead D of second amplifier stage 28 shown in FIG. 7.

VCO 26 may be conventional or as shown. The same is true of first and second amplifier stages 27 and 28, driver assembly 29 and speaker assembly 30.

OPERATION In the operation of the sound communication system 20 shown in FIG. 1, switch 76 in FIG. 2 is closed to turn the sytem 20 on. When pole 274 of switch 271, shown in control assembly 31 of FIG. 11, is moved to the last contact on the left, as viewed in FIG. 11, the public address system, i.e.. microphone assembly 33, may be used. if desired. Microphone 263, shown in FIG. 10, is used by moving the poles 259 and 260 of switch 258 into engagement with contacts 261 and 262, respectively. This places microphone 263 across the power lines through contact 262 and pole 260. At the same time, feedback is supplied over lead P1-I3A in FIG. through contact 261 and pole 259 to first amplifier stage 27 (FIG. 7) over negative feedback input junction 44 via connection from lead 12-1 shown in both FIGS. 7 and 10.

With pole 274 of switch 271 still connected to contact 277 in FIG. 11, the siren may be manually operated by depressing the button of switch 264, shown in FIG. 11. While the button is depressed, the tone which can be heard over speaker 248 in FIG. 9 will rise in pitch in a manner such as is illustrated in FIG. 15. When switch 264 is opened, the pitch of the sound emanating from the speaker 248 will follow as in FIG. 16. However, the pitch of the siren sound will not fall below point 295 of FIG. 16.

When pole 274 of switch 271 in FIG. 11 is moved to a position midway between contacts 277 and 278, at the same time, pole 275 of switch 272 is moved into engagement with contact 283, pole 275 receives the output of radio 32 over lead 41 and resistor 292 connected in that order from radio 32 to contact 283 of switch 272 in FIG. 11. In this position, pole 276 of switch 273 engages contact 288 and passes the negative feedback signal from lead P1-13B of speaker assembly 30 (FIG. 9) to input lead 13-3 of first amplifier stage 27 shown in FIG. 7.

Although pole 276 has six positions, note will be taken that lead P1-13B is not connected to any other lead, except to lead 13-3 and that only when pole 276 lies in engagement with contact 288.

As shown in FIG. 11, contacts 282, 285, 286 and 287 are all connected from the ouput of VCO 26 (FIG. 6) over lead 13-20B therefrom.

No contact need be provided at 284 for pole 275 to engage because nothing need be connected to any contact at the position 284 of pole 275 of switch 272.

With the poles 274, 275 and 276 of the respective switches 271, 272 and 273 in the positions shown in FIG. 11, the control assembly 31 is in the OFF position.

When the pole 274 of switch 271 in FIG. 11 engages contact 279, speaker 248 produces a siren sound which is in common use today.

When pole 274 engages contact 280, speaker 248 produces a sound which is commonly used on board ship in the U.S. Navy to signal an emergency.

When pole 274 is placed in engagement with contact 281, the speaker 248 produces a sound which is commonly used in European countries.

Lamps 272' and 273' in FIG. 11 are employed to indicate that relay 51 in FIG. 2 has been energized. That is, lamps 272 and 273 become illuminated when relay 51 is energized.

Lamp 271, shown in FIG. 11, becomes illuminated when switch 76 in FIG. 2 is closed. Lamp 271 thus signals the closure of switch 76.

Each of the AUTO, Hl-LO and YELP multivibrators are constructed to produce a periodic output signal susceptible to Fourier analysis.

Some of the prior art related to the field of the present invention, but not to the invention per se. includes U.S. Pat. No. 3,l37,846. Other prior art includes Electronic DesignZO, Sept. 27, I967.

If desired, all the multivibrators disclosed herein may be conventional or of a type and for use with operational amplifiers identified herein as differential amplifiers disclosed in the book Operational Amplifiers by L. P. Hullsman (McGraw-Hill Book Co., 1971).

From the foregoing, it will be appreciated that the adjustment of potentiometer in FIG. 2 does not adjust the radio volume but adjusts only the public address system volume. If desired, potentiometer 75 in FIG. 2 may be turned to produce the lowest volume possible during use of the system 20 as a public address system and when switch 76 in FIG. 2 is closed, the manual use of the siren is desired.

None, one, two or three of V,,,,, V and V,,,;, in FIG. 15 may or may not be different from V,,,,, V, and V respectively, shown in FIG. 16, and vice versa.

The phrases power supply and power supply as sembly" are hereby defined for use herein and for use in all the claims to mean a power supply that may or may not include a battery or the like.

The followiing includes some typical circuit values:

200 microfarads, 15 volts 200 microfarads, 15 volts 4 microfarads. l5 volts 2 microfarads, volts 100 microfarads, 15 volts 2 microfarads, 15 volts Capacitor 69 Capacitor 70 Capacitor 90 (for AUTO) Capacitor 90 (for YELP) Capacitor 101 (for AUTO) Capacitor 101 (for YELP) Resistor 96 (for AUTO) Resistor 96 (for YELP) Resistor 98 (for AUTO) Resistor 9B (for YELP) Resistor 99 (for AUTO] Resistor 99 (for YELP) 510,000 ohms, A watt, 5 percent 68,000 ohms, V4 watt, 5 percent 56,000 ohms, /1 watt, 5 percent 30,000 ohms, V4 watt, 5 percent 47,000 ohms, watt, 5 percent 30,000 ohms, V. watt, 5 percent Source of potential 61 12 volts Transistor 134 2N4403 Transistor 207 2N440l Resistor 100 (for AUTO) Resistor 100 (for YELP) Resistor 102 (for AUTO) Resistor 102 (for YELP) Resistor 103 (for AUTO) Resistor 103 (for YELP) Resistor 117 Resistor l 18 30,000 ohms, V. watt, 5 percent 30,000 ohms, V4 watt, 5 percent 100,000 ohms, A watt, 5 percent 680,000 ohms, A watt, 5 percent 270,000 ohms, A watt, 5 percent 300,000 ohms, A watt, 5 percent 30,000 ohms, A watt, 5 percent 30,000 ohms. A watt, 5 percent Resistor 120 360,000 ohms, V4 watt, 5 percent Resistor 121 680,000 ohms, V1 watt, 5 percent Resistor 122 270,000 ohms, Vt watt, 5 percent Resistor 130 390 ohms, 12 watt, 5 percent Resistor 138 130,000 ohms, 56 watt, 5 percent Resistor 139 160,000 ohms, A watt, 5 percent Resistor 141 10,000 ohms, 16 watt, 5 percent Resistor 142 150,000 ohms, V4 watt, 5 percent Resistor 158 6,800 ohms; V4 watt, 5 percent Resistor 159 5,100 ohms, V4 watt, 5 percent Resistor 171 100,000 ohms, V4 watt, 5 percent Resistor 179 1,500 ohms, V4 watt, 5 percent Resistor 185 130,000 ohms, V4 watt, 5 percent Resistor 187 200,000 ohms, V4 watt, 5 percent 68,000 ohms, /4 watt, 5 percent 68,000 ohms, Vs watt, 5 percent 100 ohms, /2 watt, t 10 percent 100 ohms, 1% watt, t 10 percent Resistor 205 Resistor 206 Resistor 237 Resistor 238 0,1 microfarad, 12 volts 0.1 microfarad 0.1 microfarad Capacitor C Capacitor C,, Capacitor C Potentiometer 75 250 ohms Resistor R,, 750 ohms, V4 watt Transistor 239 21 13055 Transistor 240 2N3055 The phrase means to provide DC. power" is hereby defined for use herein and for use in all the claims to mean either a DC. source of potential, an equivalent thereof or merely two conductive leads.

Preferably, radio 32, shown in FIG. 1, is grounded at 40. The ground at 40 preferably is the same chassis ground that is provided from terminal 63 in FIG. 2 and from winding 52 of relay 5] in FIG. 2.

As stated previously, VCO 26, shown in FlG. 6, may provide an output signal which may or may not be a saw-tooth. In any event, the frequency of the output signal of VCO 26 which appears on output lead J3-20B therefrom, as shown in FIG. 6, can follow, as is known, the amplitude of the DC. voltage input thereto. This following action may be faithful or approximate. However, normally, the output signal of VCO 26, shown in FIG. 6, may be one or the sum of two or more sine waves, the frequency of at least one of which preferably is approximately proportional to the amplitude of the DC. input voltage to the VCO 26. if desired, the output signal of the VCO 26 may have at least a fundamental frequency which is directly proportional to the amplitude of the DC. voltage impressed upon the input thereof.

The phrase means connecting," as used herein and as used in all the claims in any of its grammatical forms, is hereby defined to include any resistor, any transistor, any switch, any conductor or any other component, or otherwise,

The phrase ramp voltage is hereby defined for use herein and for use in all the claims to mean either a voltage which increases at least over a portion thereof for a predetermined time interval, or a voltage which decreases at least over a portion thereof during a pre determined time interval. The said ramp voltage," as defined above, may or may not be linear during the time that the ramp is increasing or decreasing.

Diode 65, shown in FIG. 2, may be shorted out and omitted in some cases, if desired.

The phrase in series" is hereby defined for use herein and for use in all the claims to means in any order.

The word energized," as describing a power supply or power supply assembly 2] herein and in all the claims, is hereby defined as a condition of power supply energization including, but not limited to, when battery 61, shown in FIG. 2, is connected in power supply assembly 21 as shown in FIG. 2.

What is claimed is:

l. A multipurpose sound communication system comprising: first and second oscillators having first and second output leads, respectively, said first and second oscillators producing respective first and second periodic output signals on said first and second leads thereof which have magnitudes that are first and second different predetermined functions of time, respectively', first means having an input lead, said first means being constructed to broadcast audible sound when at least one signal of an audio frequency is impressed upon said first means input lead; and a selectively operable switch having at least one pole and at least first and second contacts; and second means connecting said switch pole to said first means input lead, said first and second output leads of said respective first and second oscillators being respectively connected to said first and second switch contacts, said switch pole being movable to a first position in which said pole engages the said first switch contact without engaging the said second switch contact, and to a second position in which said pole engages the said second switch contact without engaging the said first switch contact, said third oscillator third output signal being on audio frequency signal, said second means including a third oscillator having a third output lead and a control input, said control input being connected from said switch pole, said third oscillator being constructed to produce a third periodic audio output signal on said third output lead of a frequency that is a third predetermined function of and variable with the magnitude of a signal impressed upon said control input thereto, said third oscillator output lead being connected to said first means input lead.

2. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said switch poles are in said first position thereof.

3. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speakers assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said switch poles are in said first position thereof; and a microphone, a double-pole, single-throw switch having third and fourth poles engageable with third and fourth contacts, respectively, said third and fourth poles engaging said third and fourth contacts at the same time and disengaging them at the same time, a DC. voltage source, said third pole being connected from said DC. voltage source, said microphone having one side connected to said third contact, means connecting said fourth pole to said third means first input lead, said fourth contact being connected from said speaker assembly, fourth means connecting said signal source output lead to the other side of said microphone.

4. The invention as defined in claim 3, wherein said fourth means includes a potentiometer having a winding with first and second ends and a wiper, said fourth means also including a first resistor, said winding having its first end connected to said other end of said microphone and its second end connected to a point of fixed reference potential more negative than that of said one end of said microphone, said first resistor being connected from said signal source output lead to said wiper.

5. The invention as defined in claim 4, including a power switch actuable to disconnect said microphone from said DC. voltage source by interrupting the circuit to said third pole, said power switch being ganged with said potentiometer, said second means including a resistor.

6. The invention as defined in claim 5, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said secondary winding to said speaker assem bly input, said second switch pole being connected from said first speaker lead.

7. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said switch poles are in said first position thereof, said speaker assembly including a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said secondary winding to said speaker assembly input, said second switch pole being connected from said first speaker lead.

8. The invention as defined in claim 2, wherein said second means includes a resistor.

9. A multipurpose sound communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a microphone; a double-pole, singlethrow switch having second and third poles engageable with second and third contacts, respectively, said second and third poles engaging said second and third contacts at the same time and disengaging them at the same time; and a DC. voltage source, said second pole being connected from said DC. voltage source, and microphone having one side connected from said second contact, fourth means connecting signal source output lead to the other side of said microphone, said third contact and said third pole being connected from said speaker assembly and to said third means second input, respectively, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said first switch pole is in engagement with said first switch second contact.

10. The invention as defined in claim 9, wherein said fourth means includes a potentiometer having a winding with first and second ends and a wiper, said fourth means also including a resistor, said winding having its first end connected to said other microphone end and its second end connected to a point of fixed reference potential more negative than that of the said one end of said microphone, said resistor being connected from said signal source output lead to said Wiper.

11. The invention as defined in claim 10, including a power switch actuable to disconnect said microphone from said DC. voltage source by interrupting the circuit to said second pole, said power switch being ganged with said potentiometer.

12. The invention as defined in claim 11, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said secondary winding to said speaker assembly input.

13. The invention as defined in claim 9, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driven means connecting said secondary winding to said speaker assembly input.

14. A sound communication system comprising: a power supply having at least first and second output junctions; a manual control circuit and a manually operable first switch connected in series from said power supply second junction to said power supply first junction, said manual control circuit having a first jun'ction, said first switch being manually movable to a closed position from an open position, and vice versa, said manual control circuit being actuable by manual movement of said first switch to one of said positions thereof to produce an increasng ramp voltage at said manual control circuit first junction at least during a portion of the time immediately succeeding the time that said first switch is moved to said one position thereof, said manual control circuit being deactuable by manual movement of said first switch to the other of said positions thereof to produce a decreasing ramp voltage at said manual control circuit first junction at least during a portion of the time immediately succeeding the time that said first switch is moved to said other position thereof; a voltage controlled oscillator having an input lead and an output lead; first means connecting said manual control circuit first junction to said voltage controlled oscillator input lead; and second means connected from said voltage controlled oscillator output lead for producing an audible sound which has a frequency spectrum that is the same as that which appears at the output of said voltage controlled oscillator.

15. The invention as defined in claim 14, wherein said first means includes an automatically deactuable electronic switch responsive to the voltage on said manual control circuit first junction for disconnecting said manual control circuit first junction from said voltage controlled oscillator input lead when said decreasing ramp voltage falls to a predetermined level.

16. The invention as defined in claim 14, wherein said manual control circuit includes a second junction, a first resistor connected between said power supply first output junction and said second junction, an auxiliary resistor connected from said second junction to said power supply second outputjunction; a diode connected between said manual control circuit second junction and said manual control circuit first junction, a second resistor and a first capacitor connected in parallel from said manual control circuit first junction to said power supply second output junction, and a third resistor connected from said first switch to said manual control circuit first junction, said first switch and said third resistor being connected in series from said power supply first output junction.

17. The invention as defined in claim 16, wherein said first means includes a first transistor having a collector, an emitter and a base, said first transistor emitter being connected from said manual control circuit first junction, a fourth resistor connected from said second junction to said first transistor base, and a fifth resistor connected from said transistor collector to said voltage controlled oscillator input lead.

18. The invention as defined in claim 17, wherein said power supply, when energized, produces first and second D.C. potentials at said first and second output junctions thereof, respectively, said first DC. potential being positive with respect to said second DC. potential, said diode having an anode connected from said second junction, and a cathode connected to said manual control circuit first junction, said first transistor being of the PNP conductivity type.

19. The invention as defined in claim 18, wherein said voltage controlled oscillator includes a differential amplifier, a unijunction transistor, second and third capacitors, and sixth and seventh resistors, said amplifier having inverting and noninverting input leads, and an output lead, said unijunction transistor having an emitter, and first and second bases, said power supply having a third output junction ofa potential which is equal to one-half the sum of the potentials of said first and second power supply junctions, the noninverting input lead to said amplifier being connected from said power supply third output function, said fifth resistor being connected from said first transistor collector to said amplifier inverting input lead, said seventh resistor and said second capacitor being connected in series from said amplifier output lead to said second means, said third capacitor being connected between said amplifier inverting input and output leads, said unijunction transistor first base and emitter being connected from said amplifier inverting input and output leads, respectively, said sixth resistor being connected from said power supply first output junction to said unijunction transistor second base. 

1. A multipurpose sound communication system comprising: first and second oscillators having first and second output leads, respectively, said first and second oscillators producing respective first and second periodic output signals on said first and second leads thereof which have magnitudes that are first and second different predetermined functions of time, respectively; first means having an input lead, said first means being constructed to broadcast audible sound when at least one signal of an audio frequency is impressed upon said first means input lead; and a selectively operable switch having at least one pole and at least first and second contacts; and second means connecting said switch pole to said first means input lead, said first and second output leads of said respective first and second oscillators being respectively connected to said first and second switch contacts, said switch pole being movable to a first position in which said pole engages the said first switch contact without engaging the said second switch contact, and to a second position in which said pole engages the said second switch contact without engaging the said first switch contact, said third oscillator third output signal being on audio frequency signal, said second means including a third oscillator having a third output lead and a control input, said control input being connected from said switch pole, said third oscillator being constructed to produce a third periodic audio output signal on said third output lead of a frequency that is a third predetermined function of and variable with the magnitude of a signal impressed upon said control input thereto, said third oscillator output lead being connected to said first means input lead.
 2. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead theReto when said switch poles are in said first position thereof.
 3. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speakers assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said switch poles are in said first position thereof; and a microphone, a double-pole, single-throw switch having third and fourth poles engageable with third and fourth contacts, respectively, said third and fourth poles engaging said third and fourth contacts at the same time and disengaging them at the same time, a D.C. voltage source, said third pole being connected from said D.C. voltage source, said microphone having one side connected to said third contact, means connecting said fourth pole to said third means first input lead, said fourth contact being connected from said speaker assembly, fourth means connecting said signal source output lead to the other side of said microphone.
 4. The invention as defined in claim 3, wherein said fourth means includes a potentiometer having a winding with first and second ends and a wiper, said fourth means also including a first resistor, said winding having its first end connected to said other end of said microphone and its second end connected to a point of fixed reference potential more negative than that of said one end of said microphone, said first resistor being connected from said signal source output lead to said wiper.
 5. The invention as defined in claim 4, including a power switch actuable to disconnect said microphone from said D.C. voltage source by interrupting the circuit to said third pole, said power switch being ganged with said potentiometer, said second means including a resistor.
 6. The invention as defined in claim 5, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said seconDary winding to said speaker assembly input, said second switch pole being connected from said first speaker lead.
 7. A multipurpose communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a second switch including a pole and at least one contact, said second switch pole being ganged with said first switch pole, said switch poles being movable both from a first position to a second position and from said second position to said first position wherein said second switch pole lies in engagement with said one contact thereof when said first switch pole lies in engagement with said first switch second contact and said poles are in said first position thereof, and wherein said second switch pole lies out of engagement with said one contact when said first switch pole lies in engagement with said first switch first contact and said poles are in said second position thereof, said second switch pole being connected from said speaker assembly, said one contact of said second switch being connected to the said second input lead of said third means, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said switch poles are in said first position thereof, said speaker assembly including a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said secondary winding to said speaker assembly input, said second switch pole being connected from said first speaker lead.
 8. The invention as defined in claim 2, wherein said second means includes a resistor.
 9. A multipurpose sound communication system comprising: a signal source having an output signal of an audio frequency at least a portion of the time, said signal source having an output lead, said signal source providing said output signal thereof on said output lead thereof; a first switch having at least one pole and at least first and second contacts, said first switch first contact being connected from the output lead of said signal source; a radio having an output lead, said radio including first means for producing an audio output signal on said radio output lead; second means connecting said radio output lead to said first switch second contact; a speaker assembly including an input therefor; third means having a first input lead connected from said first switch pole and an output connected to said speaker assembly input to provide an input signal to said speaker assembly, said third means having a second input lead; a microphone; a double-pole, single-throw switch having second and third poles engageable with second and third contacts, respectively, said second and third poles engaging said second and third contacts at the same time and disengaging them at the same time; and a D.C. voltage soUrce, said second pole being connected from said D.C. voltage source, and microphone having one side connected from said second contact, fourth means connecting signal source output lead to the other side of said microphone, said third contact and said third pole being connected from said speaker assembly and to said third means second input, respectively, the construction of said speaker assembly and its connections and the construction of said third means and its connections causing negative feedback to be supplied to said third means over said second input lead thereto when said first switch pole is in engagement with said first switch second contact.
 10. The invention as defined in claim 9, wherein said fourth means includes a potentiometer having a winding with first and second ends and a wiper, said fourth means also including a resistor, said winding having its first end connected to said other microphone end and its second end connected to a point of fixed reference potential more negative than that of the said one end of said microphone, said resistor being connected from said signal source output lead to said wiper.
 11. The invention as defined in claim 10, including a power switch actuable to disconnect said microphone from said D.C. voltage source by interrupting the circuit to said second pole, said power switch being ganged with said potentiometer.
 12. The invention as defined in claim 11, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driver means connecting said secondary winding to said speaker assembly input.
 13. The invention as defined in claim 9, wherein said speaker assembly includes a speaker having first and second leads, said third means including amplifier means and a transformer having primary and secondary windings, said amplifier means having an output lead, said secondary winding being connected to said speaker assembly, one end of said primary winding being connected from the output lead of said amplifier means, said third means including driven means connecting said secondary winding to said speaker assembly input.
 14. A sound communication system comprising: a power supply having at least first and second output junctions; a manual control circuit and a manually operable first switch connected in series from said power supply second junction to said power supply first junction, said manual control circuit having a first junction, said first switch being manually movable to a closed position from an open position, and vice versa, said manual control circuit being actuable by manual movement of said first switch to one of said positions thereof to produce an increasng ramp voltage at said manual control circuit first junction at least during a portion of the time immediately succeeding the time that said first switch is moved to said one position thereof, said manual control circuit being deactuable by manual movement of said first switch to the other of said positions thereof to produce a decreasing ramp voltage at said manual control circuit first junction at least during a portion of the time immediately succeeding the time that said first switch is moved to said other position thereof; a voltage controlled oscillator having an input lead and an output lead; first means connecting said manual control circuit first junction to said voltage controlled oscillator input lead; and second means connected from said voltage controlled oscillator output lead for producing an audible sound which has a frequency spectrum that is the same as that which appears at the output of said voltage controlled oscillator.
 15. The invention as defined in claim 14, wherein said first means inclUdes an automatically deactuable electronic switch responsive to the voltage on said manual control circuit first junction for disconnecting said manual control circuit first junction from said voltage controlled oscillator input lead when said decreasing ramp voltage falls to a predetermined level.
 16. The invention as defined in claim 14, wherein said manual control circuit includes a second junction, a first resistor connected between said power supply first output junction and said second junction, an auxiliary resistor connected from said second junction to said power supply second output junction; a diode connected between said manual control circuit second junction and said manual control circuit first junction, a second resistor and a first capacitor connected in parallel from said manual control circuit first junction to said power supply second output junction, and a third resistor connected from said first switch to said manual control circuit first junction, said first switch and said third resistor being connected in series from said power supply first output junction.
 17. The invention as defined in claim 16, wherein said first means includes a first transistor having a collector, an emitter and a base, said first transistor emitter being connected from said manual control circuit first junction, a fourth resistor connected from said second junction to said first transistor base, and a fifth resistor connected from said transistor collector to said voltage controlled oscillator input lead.
 18. The invention as defined in claim 17, wherein said power supply, when energized, produces first and second D.C. potentials at said first and second output junctions thereof, respectively, said first D.C. potential being positive with respect to said second D.C. potential, said diode having an anode connected from said second junction, and a cathode connected to said manual control circuit first junction, said first transistor being of the PNP conductivity type.
 19. The invention as defined in claim 18, wherein said voltage controlled oscillator includes a differential amplifier, a unijunction transistor, second and third capacitors, and sixth and seventh resistors, said amplifier having inverting and noninverting input leads, and an output lead, said unijunction transistor having an emitter, and first and second bases, said power supply having a third output junction of a potential which is equal to one-half the sum of the potentials of said first and second power supply junctions, the noninverting input lead to said amplifier being connected from said power supply third output function, said fifth resistor being connected from said first transistor collector to said amplifier inverting input lead, said seventh resistor and said second capacitor being connected in series from said amplifier output lead to said second means, said third capacitor being connected between said amplifier inverting input and output leads, said unijunction transistor first base and emitter being connected from said amplifier inverting input and output leads, respectively, said sixth resistor being connected from said power supply first output junction to said unijunction transistor second base. 